thermal: armada: Update Kconfig and module description

Update Armada thermal driver Kconfig entry as well as the driver's
MODULE_DESCRIPTION content, now that 64-bit SoCs are also supported,
eg. Armada 7K and Armada 8K.

Use the generic term "Marvell EBU Armada SoCs" instead of listing all
the supported SoCs everywhere (excepted in the Kconfig description,
where it is useful to have a list).

Signed-off-by: Miquel Raynal <miquel.raynal@free-electrons.com>
Reviewed-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>